Thomas Mullin (sometimes cited as Mullen) was born in Dumfriesshire, Scotland to Charles Mullin and his wife Mary Jane Gunyon. He attended the same school in Dumfries as future Titanic band member John Law Hume. He would work as a pattern weaver at the same mill as his father 

By the 1911 census he was living in Itchen, Hampshire with his aunt Margaret Beattie. He was registered as an apprentice pattern maker in the shipbuilding yards. Thomas had left the weaving industry apparently due to failing eyesight and his parents had since both died. 

Thomas signed on for the Titanic as a thrid class steward. He sadly did not survive the disaster. 

He was buried in Nova Scotia and was commemorated back in Dumfries along with John Law Hume with an Obelisk. The insciption reads:

IN MEMORY OF
JOHN LAW HUME, A MEMBER OF THE BAND
AND THOMAS MULLIN, STEWARD,
NATIVES OF THESE TOWNS
WHO LOST THEIR LIVES IN THE WRECK OF
THE WHITE STAR LINER "TITANIC"
WHICH SANK IN MID-ATLANTIC
ON THE 14TH DAY OF APRIL 1912.
THEY DIED AT THE POST OF DUTY